This application claims the benefit of Japanese Applications No. 2001-249390 filed in Japan on Aug. 20, 2001 and No. 2002-136332 filed in Japan on May 10, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to the structure of a lens barrel having a movable frame member.
2. Description of the Related Art
A lens barrel having a movable frame member that has been disclosed in Japanese Unexamined Patent Application Publication No. 4-52628 has a stationary frame and a movable lens holding frame. The movable frame is advanced or withdrawn for the purpose of zooming or focusing. Two rods of a main rod and a detent sub rod are fixed to a second group-of-lenses holding frame that is one kind of movable frame. The rods are borne by the stationary frame while being permitted to freely slide. A third group-of-lenses holding frame is borne by the rods and interposed between the stationary frame and second group-of-lenses holding frame. The second group-of-lenses holding frame and third group-of-lenses holding frame are borne by the stationary frame while being permitted to freely advance or withdraw with their rotations restricted.
However, the lens barrel disclosed in the Japanese Unexamined Patent Application Publication No. 4-52628 has a drawback described below. Namely, when the second group-of-lenses holding frame is plunged into a position for collapse, if the distance to the stationary frame gets shorter than the distance thereto attained when the second group-of-lenses holding frame is located at a wide-angle photo position, the main rod juts out of the lens barrel behind the stationary frame. It is therefore necessary to preserve a space, to which the jutting main rod escapes, within a camera body with the camera body and the lens barrel joined. This restricts arrangement of components within the camera body. However, if the main rod is designed not to project toward the camera body, the overall length of the lens barrel must be increased by a length corresponding to the projection.
Accordingly, the present invention attempts to solve the foregoing problems. According to the present invention there can be provided a lens barrel whose length can be decreased with no significant restrictions imposed on arrangement of components within a camera, and whose structure is simple.
One lens barrel in accordance with the present invention includes a movable frame member and a rod member that is incorporated in the lens barrel in order to guide and permit the frame member to move along an optical axis and that is borne to be movable along the optical axis by itself. The frame member advances or withdraws while being guided by the rod member.
Another lens barrel in accordance with the present invention includes a first frame member that is movable, a rod member that is incorporated in the lens barrel in order to guide the first frame member and permit it to move along an optical axis, and a second frame member that moves relatively to the first frame member. The rod member is engaged with the first frame member and second frame member, and can freely slide along the optical axis by itself.
Other features of the present invention and advantages thereof will be apparent from the description below.